config: Add 'experimental' switch

db/config.cc

@@ -30,6 +30,7 @@
 #include "core/shared_ptr.hh"
 #include "core/fstream.hh"
 #include "core/do_with.hh"
+#include "core/print.hh"
 #include "log.hh"
 #include <boost/any.hpp>
 
@@ -432,3 +433,9 @@ boost::filesystem::path db::config::get_conf_dir() {
 
     return confdir;
 }
+
+void db::config::check_experimental(const sstring& what) const {
+    if (!experimental()) {
+        throw std::runtime_error(sprint("%s is currently disabled. Start Scylla with --experimental=on to enable.", what));
+    }
+}

db/config.hh

@@ -102,6 +102,9 @@ public:
 
     config();
 
+    // Throws exception if experimental feature is disabled.
+    void check_experimental(const sstring& what) const;
+
     boost::program_options::options_description
     get_options_description();
 
@@ -717,6 +720,7 @@ public:
     val(ring_delay_ms, uint32_t, 30 * 1000, Used, "Time a node waits to hear from other nodes before joining the ring in milliseconds. Same as -Dcassandra.ring_delay_ms in cassandra.") \
     val(developer_mode, bool, false, Used, "Relax environement checks. Setting to true can reduce performance and reliability significantly.") \
     val(skip_wait_for_gossip_to_settle, int32_t, -1, Used, "An integer to configure the wait for gossip to settle. -1: wait normally, 0: do not wait at all, n: wait for at most n polls. Same as -Dcassandra.skip_wait_for_gossip_to_settle in cassandra.") \
+    val(experimental, bool, false, Used, "Set to true to unlock experimental features.") \
     /* done! */
 
 #define _make_value_member(name, type, deflt, status, desc, ...)    \
@@ -733,5 +737,4 @@ private:
     int _dummy;
 };
 
-
 }